Heterogeneous distribution of chain mobility in nascent UHMWPE in the less entangled state
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The structure of chain entanglements in the solid state is important for revealing the relationship of structure and properties of polyolefin. In this work, low-field solid-state 1H NMR is used to study the chain dynamics of ultra-high molecular weight polyethylene (UHMWPE) in the solid state. It has been found that the relaxation distribution, analyzed by a multi-exponential inversion program, is an effective method to characterize the heterogeneous chain mobility. It is evidenced from the results that the UHMWPE in a less entangled state presents an obviously heterogeneous distribution of chain mobility in the non-crystalline phase, corresponding to its heterogeneous distribution of entangled points. In comparison, the commercial UHMWPE with a large number of entanglements shows a much more uniform mobility of the non-crystalline components. This heterogeneous distribution of chain mobility becomes even more critical after annealing the samples below the melting point, especially for the less entangled UHMWPE.
KeywordsEntanglements UHMWPE Low field NMR Relaxation distribution UPEN
The Natural Science Foundation of China (No. 21776141), the Talent Project of Zhejiang Association for Science and Technology under Grant 2018YCGC014, the Opening Foundation from Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology (ACEMT-17-01) and sponsorship by the K. C. Wong Magna Fund in Ningbo University are gratefully acknowledged.
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